This invention relates to a drive position signal apparatus for marine propulsion devices such as outboard motors, inboard/outboard drive units including marine jet propulsion drives.
Marine propulsion devices particularly for small recreational craft generally include outboard motors, stern drive units and the like, and more recently marine jet drive units. The propulsion efficiency in such drive is optimized by tilting of the propulsion unit relative to the boat hull in order to change the relative angle of the thrust forces. In conventional outboard motors and stern drive units, a hydraulic powdered trim system is provided for angular remote setting of the lower propellor unit. Similarly, in marine jet propulsion systems, the thrust forces are trimmed by the proper angular orienting of the drive jet. A steering nozzle is conveniently provided for directing of the jet laterally for steering purposes. By trimming of the position of the steering nozzle, trimming of the drive jet is obtained and once again optimize propulsion forces created for moving of the boat.
The steering and trim control are often located in a forward portion of the boat and connected by mechanical or electrical coupling means to powered means on the propulsion unit. The positioning of the aft-mounted power unit and particularly the trim positioning system desirably incorporates an indicating means at the control station to provide the operator with a continuous trim position reading. Various remote indicating devices have been suggested in which a position transducer is secured to and positioned with the propulsion unit to generate a related electrical signal connected to a remote gauge or other control at the control station.
A simple resistive sensing unit for a trim angle indicating system is disclosed in U.S. Pat. No. 3,641,965. As more fully disclosed therein, a variable resistor is secured to the horizontal trim or tilt axis of a stern drive unit. A movable tap is attached to the trim pivot shaft and positioned on the resistor to produce a signal proportional to the trim angle of the stern drive unit. U.S. Pat. No. 3,834,345 discloses a servo system for powered trim positioning of an outboard motor or similar marine drive device. Various rotary remote sensors are disclosed to generate an electrical signal compared with a preset angle-related signal established at the control station to provide a predetermined powered positioning of the drive unit. Although various systems have been provided for generating a signal in relation to the angular orientation of an outboard unit, they have been primarily developed in connection with the conventional propeller systems. They generally are mechanically coupled and must be accurately aligned at the time of installation to provide proper calibrated outputs. Further, the special construction of the various components and incorporation into the outboard unit produce additional limitations in construction of the indicating and/or control system for connection to marine jet propulsion units. U.S. Pat. No. 3,844,247 discloses a slipping clutch unit having a pair of in-line plates on the shaft unit of a signalling device which requires the provision of the additional coupling shaft and the like. Although such systems provide proper phasing, they do not provide a highly simple and low cost type of coupling which is particularly adapted to commercial implementation. There is a need for a simple and reliable position transducer for indicating the angular orientation such as the trim positioning for marine jet propulsion devices.